Special forces or special operations forces (SOF) are military units trained to conduct special operations. NATO has defined special operations as "military activities conducted by specially designated, organized, selected, trained and equipped forces using unconventional techniques and modes of employment".
Special forces emerged in the early 20th century, with a significant growth in the field during World War II, when "every major army involved in the fighting" created formations devoted to special operations behind enemy lines. Depending on the country, special forces may perform functions including airborne operations, counter-insurgency, counter-terrorism, foreign internal defense, covert ops, direct action, hostage rescue, high-value targets/manhunt, intelligence operations, mobility operations, and unconventional warfare.
